1. Field of the Invention
The present invention relates to a semiconductor light emitting device for emitting white light, and more particularly to a semiconductor light emitting device provided with a reflector for radiating heat generated in light emitting elements to outside.
2. Description of the Related Art
Nowadays, there is developed a light emitting diode (LED) chip using a gallium nitride semiconductor, which may emit blue light of high brightness. When using this gallium nitride semiconductor, the LED has a large output and less color shift in comparison with other LEDs emitting red light or yellowish-green light.
This blue light emitting diode chip is broadly used in various devices such as portable electronic equipment, a sign lamp or an indication lamp. To apply the LED chip to the above-mentioned devices, a point emission should be converted into a planar emission.
For this reason, in the prior art, a chip is installed in front of the LED chip in order to control the direction of the light (International Patent Publication WO98/5078), or a plurality of LED chips are densely arranged to form an array.
However, the dense array of the LED chips or the installation of lens causes the increase of the manufacture costs.
In addition, as the needs for the white light emission increase, there is recently proposed a light emitting device for emitting white light by placing on an LED chip a YAG:CE fluorescent substance which is capable of emitting green light by partially absorbing blue light emitted from the LED chip.
This device emits white light by mixing a YAG fluorescent substance in a sealing resin for sealing the light emitting element. However, this method has a problem that it may not give a satisfactory light output since the light transmission is limited due to the sealing resin.
In order to overcome such a drawback, there is also proposed a light emitting device which realizes white light emission by installing a reflector containing fluorescent substances around the LED chip.
For example, US Patent Publication US2003/0038295A1 discloses a light emitting device which may emit a planar white light of a large output by installing a reflector made of transparent resin and containing fluorescent substances around an light emitting element in order to reflect the blue light radiated from the light emitting element as it is or reflect it after absorbing and then converting the blue light partially into yellow light.
The reflector disclosed in the above US Patent Publication is characterized in that it functions as a fluorescent member as well as a reflecting member. However, the US Patent Publication fails to realize the reflector having a light radiating function.